The M225 cannon and M8 baseplate weigh approximately 18 pounds. This is a lightweight and highly mobile weapon that can be used in this mode on patrols with minimum deployment.

The SIGHT UNIT (M64/M64Al) (fig. 14-5) is the standard sight used with the 60-mm mortar. Once a sight has been calibrated on a mortar, it should always be used with that mortar. It is used for laying-in the mortar for elevation and deflection. The sight unit consists of a

Figure 14-5.-Sight unit (M64/M64A1).

telescope mount and a nonmaintainable elbow telescope, fastened into one unit for operation. The elbow telescope provides magnification and a line of sight from which the mortar is aimed. The elbow telescope is a 1.5-power, fixed-focus telescope. The cross lines are at right angles to each other.

The TELESCOPE MOUNT consists of the lower, center, and upper parts. The lower part contains a locking lever latch, an elevation micrometer knob with scale, and an elevation locking knob. There is also a dovetail bracket located on the right side of the mount that mates with the dovetail slot located on the yoke of the biped. A semicircular, coarse elevation scale indicates from 700 to 1,600 mils in 100-mil increments. The ELEVATION KNOB contains an elevation micrometer scale of 100 mils, numbered in l-mil increments from 0 to 100. Turning the elevation knob tilts the mount in elevation to the desired angle, as read on the coarse and micrometer elevation scales. The elevation locking knob prevents the elevation knob from rotating during firing.

The center part of the telescope mount has a deflection knob that rotates the mount for direction. A crank is provided on the knob for rapid deflection movement. The deflection locking knob locks the

Figure 14-6.-Boresight (M115).

deflection knob during firing. The coarse deflection scale is fixed to the upper parts of the center section and has 64 graduations. This scale rotates with the upper part of the telescope mount. The coarse deflection slip scale is located adjacent to the coarse deflection scale. The micrometer deflection slip scale has 100 black graduations, numbered from 0 to 100 in increments of 1 mil. The M225 cannon, the M8 baseplate, and a heat protective mitten are all that is required to use this weapon in the hand-held mode.

The BORESIGHT (Ml15) (fig. 14-6) is used to calibrate the sight for the mortar. Since no two mortars are exactly alike, each sight MUST be calibrated on its own mortar. The body of the boresight contains three level vials. They are used to determine that the angle of elevation (preset at 800 mils) and to determine that the V-slides are in a perpendicular position.

THE AIMING POST (M1A2) is used with the mortar as an aiming point. Two aiming posts are provided for each mortar. These aiming posts can be separated in the center so as to be more compact when

Figure 14-7.-A typical round of mortar ammunition.

being transported. There is a carrying bag made of canvas to hold each of the sections. The aiming posts are 8 feet long and 11/8 inches in diameter. They are painted with 5-inch red and white horizontal stripes to aid in sighting the mortar. The lower section of each aiming post has a pointed end to help place it in the ground. Most of these aiming posts become unserviceable because of improper use. These posts are hollow and can be easily bent if dropped. When positioning the posts in hard or frozen earth, you should loosen the ground with an entrenching tool before trying to seat them. Do NOT attempt to hammer the aiming posts into the ground. This may bend the sections or burr the connections, making the posts unserviceable.

The AIMING POST (M14) is used with the mortar as an aiming point. Two aiming posts are provided for each mortar. When positioning the posts in hard or frozen earth, you should loosen the ground with an entrenching tool before trying to seat them. DO NOT attempt to hammer the aiming posts into the ground. This may bend the sections or burr the connections, making the posts unserviceable.

The AIMING POST LIGHT (M58, GREEN AND M59, ORANGE) is used for night firing by clamping the light to the aiming post. You can only see the glow of the aiming post light from the direction of the mortar position. The colored lights aid the gunners in identifying their own aiming posts.